Edition 1995-2
- UNDERSTANDING MESOTHELIOMA: Special Report
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Over the last decade, concerns over the occupational health risks of asbestos inhalation have led to a false sense of security that anything non-asbestos is by definition less hazardous and safe to use. However, this simplistic assumption is inconsistent with emerging hazard and risk assessment on other natural and man-made fibres. The findings of recent studies may be surprising to many and are likely to have far-reaching regulatory implications.
OSHA scientists express concerns over fibreglass risks
Last year, a team of OSHA (U.S. Occupational Safety and Health Administration) scientists
concluded that fibrous glass, used to replace chrysotile in a variety of applications, "are
carcinogenic." In fact, their report claims, based on a comparison of the carcinogenic potency of
glass fibres and asbestos fibres (all types), that "on a fibre-per-fibre basis, glass fibres may be as
potent or more potent than asbestos." The review presented data which suggest that workers
exposed to these synthetic fibres during production may require less of a cumulative dose as
compared to asbestos for the same risk of lung cancer.
Applying the OSHA quantitative risk assessment model for asbestos to the use of synthetic mineral fibres, the authors explain that an occupational 8-hour time-weighted average exposure of 0.043 f/cc would be related to an excess lung cancer risk of 1 per 1,000 workers over a 45-year working life. OSHA considers this risk significant and requires that steps be taken to reduce the risk to workers.
Based on this analysis and the results of numerous scientific studies, the authors write: "In an
enlightened society, risk identification should be followed by proper risk communication and risk
management leading to hazard abatement in those situations where it is necessary. Addressing the carcinogenicity of glass wool and mineral wool in a responsible manner will ultimately result in the least costly avenue for society in general and will help to restore public confidence in industry and government to provide a healthful working environment."
Other substances more hazardous than chrysotile?
OSHA is not alone in raising serious concerns over the unqualified use of substitute fibres and
products. The last few years have seen a number of scientific reports whose comparisons of the
relative toxicity of chrysotile and other alternative materials raise important questions about the
issue of substitution.
Another recent U.S. study found that silicon carbide whiskers, a finely spun ceramic compound
used for insulation and a reinforcing agent in resins, metals and ceramics, has the potential to
"cause significant immediate and long-term damage" and that "it appears to be more toxic than
crocidolite." As a result, the authors recommend that these materials be handled in such a manner as to minimize pulmonary exposure. Cytotoxicity tests of aramid fibres have also indicated that these fibres can be as toxic as crocidolite and chrysotile asbestos.
One of the most extensive studies of the health effects of man-made mineral fibres is a European
cohort study of more than 25,000 workers in plants producing man-made mineral fibres. In its
most recent follow-up, the team of researchers found elevated numbers of deaths from lung cancer for rock and slag wool, glass wool and continuous filament production - with standardized mortality ratios (SMRs) of 137, 127 and 127, respectively.
Perhaps of greatest health concern are Refractory Ceramic Fibres (RCFs) which, on a fibre-per-
fibre basis, have consistently been shown to be more hazardous than chrysotile. One recent study, which compared the fibrotic and tumourogenic potential of chrysotile and RCF, found that they had similar health effects on the laboratory rats studied, despite the fact that chrysotile exposed animals received a dose more than 50 times higher than the RCF exposed animals.
A summary of some recent data comparing the toxicity of chrysotile and other fibres is presentedbelow.
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"Our review then examines the carcinogenic potency of glass fibers to humans in comparison with asbestos fibers and concludes that on a fiber-per-fiber basis, glass fibers may be as potent or even more potent than asbestos." Infante et al., Am. J. Ind. Med. (1994)
"Silicon carbide whiskers have the potential, at least, to cause significant immediate and long-term pulmonary damage. It appears to be more toxic than crocidolite." Vaughan et al., Env. Res. (1993)
"... when the fibre doses were expressed as the number of fibres per culture area, the asbestos and MMVF appeared equally effective in human mesothelial cells." Pelin et al., Environmental and Molecular Mutagenesis (1995)
"Results of cytotoxicity tests indicated that Aramid was as toxic to hamster trachael epithelial cells and rat lung fibroblast cells as were crocidolite and chrysotile asbestos when expressed on both an equal mass and equal fiber number basis." Marsh et al., Drug and Chem. Toxic.(1994)
"Exposures to these fibres should be controlled to the same degree as that required for asbestos until data supporting a lesser degree of control become available." IPCS (1993)
"Both rats and hamsters exhibited dose-dependent increases in proliferation of pleural mesothelial cells following exposure to both fibre types (MMVF and RCF-1)." Rutten et al. Fund. Appl. Tox. (1994)
"It is suggested that some types of man-made fibers have a greater ability than asbestos to induce tumors." Adachi et al., Environ. Research (1991)
Regulatory responses
As new evidence of the comparative risks of chrysotile and alternative fibres and products is made available, it is likely that regulations governing practices and exposure limits will be adapted to reflect the emerging scientific reality. In fact, recent developments in the U.S., Canada and the EC may provide some indication of the direction that has become necessary as science continues to reduce the uncertainty of the decision-making process.
As reported in recent editions of The Asbestos Institute Newsletter, some countries have begun to develop classification schemes, establish exposure limit standards and adopt codes of practice for a wide range of natural and man-made mineral fibres. These developments are an indication that regulatory agencies are beginning to respond to the scientific realities of the fibres and health issue.
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According to Dr. J.H. Duffus, Chairman of the scientific committee of the International Seminar
on Assessment of Carcinogenic Risk from Occupational Exposure to Inorganic Substances,
scientists are concerned about the conceptual confusion arising from the indiscriminate use and
meaning of the words hazard and risk.
In occupational health circles, hazard is defined as "the intrinsic property of a chemical agent with
the potential to cause harm." In contrast, risk is defined as "the likelihood that the potential for
harm will be attained under specific conditions of use and/or exposure."
In the case of asbestos, this important distinction requires that the risk be defined according to the
actual conditions of exposure (i.e., according to fibre types involved and degree of exposure). To illustrate the point, Dr. Andrew Churg of the University of British Columbia presented data on the general populations of the mining communities of Eastern Québec. Residents of these communities are exposed to atmospheric levels of chrysotile and tremolite several hundred times greater than those found in the air of most cities in North America. While this results in increased pulmonary concentrations of chrysotile and tremolite, some 5 to 10 times higher than are seen in residents of most major cities, repeated epidemiological studies of persons living for whole lifetimes in the mining townships have thus far failed to show an increased incidence of either lung cancer or mesothelioma.
For Dr. Churg, these are important observations because they indicate that lifetime chrysotile and
tremolite burdens, considerably greater than those in the general population of North American
cities, do not produce detectable asbestos-related malignancies. These findings, according to Dr.
Churg, provide support for the conclusion that the much lower urban ambient or asbestos insulated building levels of chrysotile to which everyone in the population is exposed do not cause adverse effects. Thus, without denying the "hazard" (potential to cause harm) of asbestos, the "risk" (likelihood that the potential is attained) of exposure to the chrysotile fibre type at low levels is put in perspective.
Finally, Dr. Churg indicated that from a regulatory perspective, currently regulated occupational
exposure limit values for chrysotile (ex.: 1 f/cc), appear to be adequate to control for asbestosis,
lung cancer and mesothelioma.
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Emerging risk assessment evidence is cause for reflection. One can recall all too vividly the fervor of regulators in some countries to ban all types and uses of asbestos ‹ driven by perceived high risks associated with asbestos and the belief that non-asbestos fibres and products are less hazardous.
For example, in the case of the United States, the Environmental Protection Agency did not
consider the potential harm from the increased use of products designed to substitute for asbestos
when developing its ban and phase-out rule. The Agency justified its position by stating that "it
has more concern about the continued use and exposure to asbestos than it has for the future
replacement of asbestos with other fibrous substitutes."
It is ironic that less than 10 years later, scientists at its sister agency, OSHA, published a study that concludes that "on a fiber per fiber basis, glass fibers may be as potent or even more potent than asbestos." Other scientific studies on a variety of fibres confirm that the asbestos family of fibres is not unique in its ability to cause fibrosis and tumours. These findings underscore the wisdom of the U.S. Court which, in overturning the EPA's asbestos ban rule, concluded that a ban "actually may increase the risk of injury that Americans face."
Emerging evidence also raises a cautionary flag for regulators in other countries. Indeed, careful
consideration must now be given regarding how best to maximize limited public and occupational
health resources ‹ further restrictions on the use of asbestos or comprehensive controls on all
respirable and durable fibres?
Further restrictions on chrysotile asbestos unwarranted
Today, the prevailing view is that the health hazards of asbestos differ by fibre type and product
type. This has led to regulations which call for a total ban on the amphibole forms of asbestos and low-density insulation materials. There is, however, a broad scientific consensus that if properly controlled and used, chrysotile and current chrysotile-based products such as asbestos-cement, friction materials and other high-density products do not present risks of any significance to public or worker health. This position is supported by growing scientific evidence of a threshold level of occupational exposure to chrysotile which is higher than current international exposure limit standards. (The threshold issue was dealt with in some detail by Dr. Kevin Browne in the March 1994 edition of The Asbestos Institute Newsletter).
This evidence begs an obvious question. What additional public health benefits can be gained by
imposing further restrictions on chrysotile?
The notion of opportunity cost
While the evidence strongly suggests that further lowering controls for chrysotile would have no
detectable impact on worker or public safety, it is clear that it would have significant costs to
society. According to health economist Richard Belzer, moving from a 2 f/cc occupational
exposure limit to a 0.2 f/cc limit costs more than $65 million (U.S.) per hypothetical premature
death averted, a level he understatedly calls "an inefficient allocation of resources."
In the U.S., the Court of Appeals came to similar conclusions regarding the costs and benefits of a ban rule. "The benefits seem far outweighed by the costs," explained the Court in light of the
EPA's admission that to avoid three hypothetical cancer cases, its ban of asbestos-cement pipe
would cost between $128-$227 million (U.S.). These cost estimates are considered conservative, given that the asbestos risk model used is based on a linear, no-threshold model which also fails to take into account fibre-type difference.
In comparison, a recent study by Duke University researchers estimated that the average cost of
saving a life is approximately $19,000 for medical care and $48,000 for injury reduction.
Towards a more balanced approach
When compared to other public policy initiatives or workplace restrictions, it is clear from a
societal standpoint that little can be gained from further restrictions on chryso-tile. However, the
same cannot be said about other natural and man-made fibres.
The preoccupation of regulatory authorities with asbestos has directly or indirectly forced users to switch from one substance, which is stringently controlled, to others which are not. Moreover, the false perception that fibres other than asbestos are safe has led, in some cases, to indiscriminate use, often with little attention paid to the need for prevention and control measures to protect worker health. This is no longer acceptable in light of emerging risk assessment evidence.
Recognizing that this situation can no longer be tolerated, some countries have begun to introduce classification schemes which take into consideration the cancer- causing potential of many other natural and man-made fibres, introduce exposure limit values and develop codes of practice for their safe use. However, in many other countries, including the U.S.A., no exposure limit values have yet been established.
Rather than imposing further restrictions on chrysotile, perhaps society would be better served if
the control models developed for chrysotile were adapted and applied to other natural and man-
made fibres. In this respect, one cannot overlook the sage advice of the IPCS Group of Experts
Report on Organic Fibres which concluded that "exposures to these [respirable and durable] fibres should be controlled to the same degree as that required for asbestos until data supporting a lesser degree of control become available."
Scott Houston
Director General
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This 9th Conference was attended by delegates from various asbestos industries and mining
interests, representatives from regional, national, and international labour organizations, and
emissaries from numerous governments. In addition to providing an overview of scientific and
regulatory developments, this year's conference placed special emphasis on dust control,
environmental management, and product technical and performance issues.
Controlled use: scientific perspectives
The 9th Biennial Conference brought together a number of internationally respected scientists and
industrial hygienists to discuss their perspectives on controlled use.
Dr. Graham Gibbs gave a detailed overview of the health-related effects of mineral fibres, which included an update of peer-reviewed data demonstrating the recognized differences in potency between the different asbestos fibre types. Dr. Jacques Dunnigan also discussed evidence of a "no observable effect threshold" for chrysotile at exposure levels consistent with occupational exposure limit values currently in place in most countries of the world (i.e., 1 f/cc). Representatives from the ILO, IARC and the EC each shared their perspectives on the controlled-use philosophy and its place in the regulation of
chrysotile asbestos and other carcinogenic substances.
Putting theory into action
Discussing the practical implications of the controlled-use approach, Mr. Serge Trudel of the
Québec Federation of Labour (QFL) demonstrated how it has been successfully implemented in the Québec chrysotile mining sector resulting in low levels of exposure. "These low levels of
exposure will, in our opinion, practically reduce to zero, or close to it, the risk of asbestosis, lung cancer and mesothelioma", he explained. Mr. Trudel also discussed a recent international initiative to develop a model Code of Practice for the Safe Use of Manufactured Vitreous Fibres.
Other presentations highlighted the efforts which have been made and continue to be made towards technical improvements for dust monitoring and control and waste management across various sectors of the chrysotile industry. In fact, the most recent AIA survey found that 96% of member companies operated at or below 1 f/cc.
Initiatives described by a number of companies demonstrate how the industry adheres to the
principle of sustainable development by reducing waste, energy consumption, water usage, etc. A number of speakers described the challenges they sometimes face in implementing environmental corporate policy. The success of many such initiatives suggests that with commitment, discipline and training, the chrysotile asbestos industries can be models of environmental control and industrial hygiene.
Product perspectives
While the success of controlled-use initiatives is in large measure responsible for the relative
regulatory stability which delegates described, a number of presentations also demonstrated that
cost and performance of chrysotile products, compared to many substitutes, is an increasingly
important factor - particularly in light of growing concerns over the health and safety of many of
these substitute fibres and products.
For example, in the case of a/c sheet, Indian industry enjoys significant cost and performance
advantages over competitive products such as galvanized iron and aluminum sheets. In addition,
new technologies are being developed to maximize the use of fly ash in a/c formulations in order to improve even further the cost-benefit advantages.
In the case of brake linings, many of the difficulties associated with non-asbestos products were
reviewed. It was felt that increased awareness regarding the health risks of alternative fibres and
performance shortcomings of non-asbestos linings will result in a more level playing field, thus
enhancing the future prospects of chrysotile friction products. Similarly for gaskets, the failure of certain non-asbestos formulations, particularly in high-temperature applications and the difficulty in matching the performance and price characteristics of chrysotile-based gaskets is ensuring continued demand.
A number of product and technological developments were also described by the speakers. These include: a total roofing system for pitched roofs on residential buildings in which an asbestos-cement product provides customers with an attractive, high-quality, and long-lasting roofing system at minimal cost; and engineering improvements in friction materials manufacturing, with emphasis on pre-molding technology that significantly reduces dust levels and installation effort. Several presentations stressed the energy efficiency of chrysotile-cement products compared to many alternative materials.
Keys to progress in the 90s
The final session of the Conference examined what action the international asbestos industries must take to ensure world-wide application of the principles of responsible use. Industry leaders from both the mining and manufacturing sectors pledged their commitment to work towards a world industry that is clean and transparent beyond reproach. A most notable outcome of this session was that mine representatives from Canada, Brazil and Zimbabwe agreed in principle to develop a range of new responsible-use initiatives.
Copies of the proceedings are available through
AIA € 10, rue de la Pépinière € 75008 Paris € France
tel.: (33.1) 45.22.14.00, fax: (33.1) 42.94.98.86
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No risks to the public
Mr. Justice Drost dismissed in their entirety, all claims made by a Vancouver real estate firm that
sought $11 million in damages from W.R. Grace & Co., a manufacturer of sprayed-on asbestos
insulation product used extensively in the 1970s. After hearing close to two years of testimony and deliberating on the evidence presented for 19 months, he concluded that the plaintiffs had "failed on all counts" to prove that the asbestos insulation materials contaminated the buildings and that as a result, building workers and occupants had been exposed to an increased risk of asbestos-related disease.
In arriving at that conclusion, Mr. Justice Drost dismissed the views of plaintiff experts who
claimed that there is no safe level of exposure to asbestos. Experts for the defendants
demonstrated that the levels of asbestos fibre typically found in buildings are not significantly
different than airborne concentrations found in the air outside these buildings (e.g., 0.0002 f/cc).
They also explained that it takes "an enormous burden" of inhaled fibre to generate an increased
risk of asbestosis, mesothelioma or lung cancer in man - requiring exposure over prolonged
periods of time at levels up to 100,000 times higher than those typically found in buildings.
In his judgement, Mr. Justice Drost also referred to expert testimony which suggests that asbestos is not the only cause of mesothelioma (a rare cancer of the membrane lining of the chest or abdominal cavities). The evidence presented found that only 60% to 70% of mesotheliomas are attributable to asbestos exposure, and that almost all of these are a result of exposure to amphibole asbestos varieties. This led Mr. Justice Drost to conclude that "the actual risk of contracting mesothelioma from chrysotile asbestos fibres is at worst minimal and at best non-existent".
Evidence of a safe level of exposure
Evidence was also presented before the Court which supports the existence of a level of exposure
to chrysotile asbestos below which there is no risk of contracting any asbestos-related disease, and that this level is higher than current occupational exposure limit standards. This is in part
explained by the fact that, in contrast to the amphiboles, chrysotile, once inhaled, is very rapidly
removed from the lungs by the body's natural defence mechanisms. The significance of this
testimony is that exposure levels typically found in buildings are up to 10,000 times lower than
today's occupational exposure limits. It also holds considerable importance for industry, as
chrysotile accounts for more than 99% of present-day asbestos production and use.
Mr Justice Drost's findings stand in stark contrast to public perceptions on asbestos health risks.
According to one expert,"the popular press has been influenced by too much noise about asbestos in a way that people regard asbestos with an unholy fear. And there is no basis for doing so." Industry sources hope that the decision will serve to instill some calm and reason into the asbestos in buildings issue that is long overdue - and that it will build confidence in today's chrysotile products and the fact that appropriate preventive and control programmes provide more than adequate protection to workers.
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